SO2 effect on 304 and 316

[matmat]

I am looking at the possibility of replacing 316 stainless with 304 on a machine processing food which has been treated with SO2 as a preservative. Can anyone advise me on whether this is suitable given that the machine will operate in the temperature range -18 to +45 degrees Celcius in all humidity conditions and whether I have to worry about Sulphuric Acid formation and consequent attack of the 304 in these conditions? Will 304 do the job?

 

[Metalguy]

You need to know what your Cl amounts are. That makes a big difference between the two SSs.

In general, stay with 316 if you can, tho.

 

[jverly]

Coming from the corn wetmilling industry, which heavily uses SO2 in the process, I would highly suggest 316L materials. The 316 will have a higher resistance to and corrosional issues with the SO2 and going to 316L will reduce and carbide precipitation during construction. Any precipitation during the fabrication will induce cracking of the joint and weeping of the remaining carbon in the hot work area - ultimately leading to pinhole leaks and a cracked joint.